This invention relates to aqueous base, metal working lubricating compositions. More particularly, it relates to improved multipurpose waterbase metal cutting fluids for use in cutting, drilling, reaming and other machining and forming operations of ferrous and non-ferrous metals.
Cutting fields may be divided into two broad classes; mineral-oil fluids and soluble-oil fluids. The former are based on mineral-oil stocks, and are compounded in a ready-to-use form, while the latter are based on mineral oil, or other, stocks and are compounded as concentrates to be diluted with water at the point of use. Both classes of fluids frequently employ sulfur-, chlorine-, and phosphorus-containing additives as cutting aids. Which class of cutting fluid should be used in a given application depends generally upon whether the overall operation is best served by emphasizing lubrication (as with a mineral-oil fluid) or by emphasizing cooling (as with a soluble-oil fluid).
Soluble oils have been further divided into three, oftentimes rather indistinct, classes: heavy-duty, general-purpose, and synthetic fluids. When mixed with water these oils form emulsions which can range from true emulsions, as in the case where the soluble oils contain mostly oil-soluble components, to nearly true solutions, as in the case where the soluble oils contain mostly water-soluble components. In general, cutting fluids made from heavy-duty and general-purpose soluble oils are characteristically emulsion-like, while those made from synthetic soluble oils are solution-like, although it should be understood that the whole range of types of mixtures is possible. The term soluble oil is used herein to denote the fluid prior to dilution with water; after dilution, the fluid is called either an emulsion or a cutting fluid.
Heavy-duty fluids (sometimes called "semi-synthetic fluids") are opaque or translucent emulsions that contain some mineral oil in addition to antirust, extreme pressure (EP), antiwear and possibly antifoam and bactericide additives. These fluids are intended for all-purpose cutting.
General-purpose fluids are opaque emulsions of mineral oil, rust inhibitor additives and possibly antifoam and bactericide additives. These fluids are mainly intended for use as a low-cost cutting fluid in non-severe operations.
Synthetic fluids are transparent or translucent but possibly colored solutions or colloidal dispersions of chemicals which contain no mineral oil. These fluids are intended for heavy duty general use and are most often used for grinding operations.
A very effective soluble oil may be prepared using petroleum sodium sulfonate anionic surfactants as an emulsifier. The sulfonates, along with coemulsifying agents, effectively emulsify the LVI base oils and other water insoluble components used in metal-working fluids. The coemulsifier system, which is known as the soluble oil base, enhances the emulsification performance of the sodium sulfonates and may consist of several different components balanced for the best overall results. General purpose soluble oils contain only base oil plus emulsifiers and their dilute emulsions contain relatively low concentrations of oil. Thus, they have only modest lubrication properties and serve mainly as coolants in metalworking operations. On the other hand, heavy duty soluble oils contain extreme pressure and antiwear additives (fatty materials and sulfur and chlorine-containing compounds) in addition to the base oil and emulsifiers. Thus, their overall metal cutting performance will be much better than that of a general purpose fluid and in rich emulsions will approach that of a neat oil.
Improved performance can be achieved by increasing the additives and/or oil concentration of the cutting fluid. However, this option greatly increases the cost of the cutting field. Thus, a need exists for an improved cutting fluid that has good antirust performance, longer service life and substantially better tool life at high dilution rates. It should also be suitable for grinding operations as well as other machining operations.
The most important characteristic of a metal-cutting fluid is its ability to aid the metal-cutting process; the extent to which it aids this process is usually measured in terms of some combination of the rate of removal of metal, the life of the cutting tool, and the surface finish of the machined part.
It is known, e.g., U.S. Pat. No. 3,509,052, which is incorporated herein by reference, that polyoxyalkylene glycols are useful as demulsifiers in lubricating oil for internal combustion engines.
It is also known, e.g., U.S. Pat. No. 2,958,661, which is incorporated herein by reference, that water soluble non-ionic compounds such as a block polymers of ethylene oxide and propylene oxide are useful as wetting, buffering, solubilizing and load carrying agents in water solutions. However, it was found that such non-ionic compounds were either ineffective in activating the extreme pressure properties of polyalkali metal salts or produce a detrimental effect such as foaming or solution instability.
Surprisingly, I have now found that block copolymers of ethylene oxide and propylene oxide or other alkylene oxides, generally known as polyalkylene glycols, are very effective in improving the metal-cutting ability of an emulsion-type soluble oil.